Probing Oxygen-to-Hydrogen Peroxide Electro-Conversion at Electrocatalysts Derived from Polyaniline.

Hydrogen peroxide (H2O2) is a key chemical for many industrial applications, yet it is primarily produced by the energy-intensive anthraquinone process. As part of the Power-to-X scenario of electrosynthesis, the controlled oxygen reduction reaction (ORR) can enable the decentralized and renewable production of H2O2. We have previously demonstrated that self-supported electrocatalytic materials derived from polyaniline by chemical oxidative polymerization have shown promising activity for the reduction of H2O to H2 in alkaline media. Herein, we interrogate whether such materials could also catalyze the electro-conversion of O2-to-H2O2 in an alkaline medium by means of a selective two-electron pathway of ORR. To probe such a hypothesis, nine sets of polyaniline-based materials were synthesized by controlling the polymerization of aniline in the presence or not of nickel (+II) and cobalt (+II), which was followed by thermal treatment under air and inert gas. The selectivity and faradaic efficiency were evaluated by complementary electroanalytical methods of rotating ring-disk electrode (RRDE) and electrolysis combined with spectrophotometry. It was found that the presence of cobalt species inhibits the performance. The selectivity towards H2O2 was 65-80% for polyaniline and nickel-modified polyaniline. The production rate was 974 ± 83, 1057 ± 64 and 1042 ± 74 µmolH2O2 h-1 for calcined polyaniline, calcined nickel-modified polyaniline and Vulcan XC 72R (state-of-the-art electrocatalyst), respectively, which corresponds to 487 ± 42, 529 ± 32 and 521 ± 37 mol kg-1cat h-1 (122 ± 10, 132 ± 8 and 130 ± 9 mol kg-1cat cm-2) for faradaic efficiencies of 58-78%.

Advances in Methanol Production and Utilization, with Particular Emphasis toward Hydrogen Generation via Membrane Reactor Technology.

Methanol is currently considered one of the most useful chemical products and is a promising building block for obtaining more complex chemical compounds, such as acetic acid, methyl tertiary butyl ether, dimethyl ether, methylamine, etc. Methanol is the simplest alcohol, appearing as a colorless liquid and with a distinctive smell, and can be produced by converting CO2 and H2, with the further benefit of significantly reducing CO2 emissions in the atmosphere. Indeed, methanol synthesis currently represents the second largest source of hydrogen consumption after ammonia production. Furthermore, a wide range of literature is focused on methanol utilization as a convenient energy carrier for hydrogen production via steam and autothermal reforming, partial oxidation, methanol decomposition, or methanol⁻water electrolysis reactions. Last but not least, methanol supply for direct methanol fuel cells is a well-established technology for power production. The aim of this work is to propose an overview on the commonly used feedstocks (natural gas, CO2, or char/biomass) and methanol production processes (from BASF-Badische Anilin und Soda Fabrik, to ICI-Imperial Chemical Industries process), as well as on membrane reactor technology utilization for generating high grade hydrogen from the catalytic conversion of methanol, reviewing the most updated state of the art in this field.